Method for the centrifugal continous casting of metals



June 14, 1960 J. DAUBERSY EI'AL 2,940,143

METHOD FOR THE CENTRIFUGAL CONTINUOUS CASTING OF METALS Filed Oct. 30, 1957 4 Sheets-Sheet 1 INVENTORS 4/54, (46,, MXW

ATTORNEYS June 14, 1960 J, DAUBERSY ETAL 2,940,143

METHOD FOR THE CENTRIFUGAL CONTINUOUS CASTING 0F METALS Filed Oct. 30, 1957 4 Sheets-Sheet 2 ill Q INVENTORS )ATTORNEYSV METHOD FOR THE CENTRIFUGAL CONTINUOUS CASTING 0F METALS Filed Oct. 30, 1957 June 14, 1960 J, D R EI'AL 4 Sheets-Sheet 3 M, 4, JMKM ATTORNEYS June 14, 1960 J, DAUBERSY EIAL 2,940,143

METHOD FOR THE CENTRIFUGAL CONTINUOUS CASTING 0F METALS Filed 061.. 30, 1957 4 Sheets-Sheet 4 ll l ln ll' ll lllI I] @Ms -M ATTORNEY 5' United States Patent METHOD FOR THE CENTRIFUGAL CONTINOUS CASTING or METALS Jean Daubersy, 21 Rue Nicolay, Seraing, Belgium, and Albert Schlemmer, 323 Rue de lYser, Ans, Belgium Filed October 30, 1957, 521'. N0. 693,380 Claims priority, application Belgium, November 9, 1956 5 Claims. (Cl- 22-2001) The present invention, made by MM. lean Daubersy and Albert Schlemmer, relates to the centrifugal casting of metals, and more especially to the centrifugal casting of steel, said casing being realized either by means of an exterior mould or better between two concentric moulds.

invention may be used specially in the process previously described by the same inventors and forming the subject of co-pendin'g British application No. 9970/57.

In order to facilitate an intelligent understanding hereof, the explanations and designs of the present specification relate to the centrifugal casting processes for steel using concentric moulds.

The invention consists in interposing a liquid ring formed by a melted metal heavier than steel between the exterior mould and the centrifuged circular piece.

This ring functions as a lubricant to reduce considerably the friction between the exterior mould and the centrifuged circular piece by reduction of the contact between the centrifuged circular piece and the solid wall of the mould.

According to the invention, the metal to be used in order to form the liquid ring is selected not only by its density, but also by its melting and ebullition temperature. 1

Indeed, the metal of the ring must melt at a temperatu're inferior to the melting point of the steel, in order that this metal may remain liquid at the temperature existing in the ring and resulting from the contact with the cooled'mould on the one hand and with the solidifying steel on the other hand.

It is also necessary that the metal does not begin to boil, that is to say that itsebullition point at'the pressure generated by the centrifuging must be superior to the melting point of the steel or at least to the highest temperature which may exist at its contact with the solidified wall of the steel.

Besides, according to the invention, the metals used must not contaminate the steel. These conditions may be realized only by a small number of metals.

7 The use of the following metals is especially claimed: lead, bismuth, silver and the alloys essentially constituted by these metals. The practical realization must also take the other characteristics proper to these metals and to their alloys into account and-more especially their thermal conductivity, their specific heat, their ability to oxidize in the air, their degree of'toxity, their action on the metals used for the manufacture of the moulds, and their aptitude for handling in liquid condition bypumps and pipes. V

7 .According to the invention, the liquid ring is a simple means to avoid the danger of fissuring of the caststeel, said danger being due to the shrinkage resulting from the solidification and from the cooling.

This danger of fissuring is more'especially important as the centrifugal force is opposed to the shrinkage and it is evident that fissuring can only be avoided if the profile of the mould fits with a sulhcient precision the 2,940,143 Patented June 14, 1960 profile resulting from the natural shrinkage. In the case of a solid mould, this involves difiicult problems of regulation which disappear or are considerably alleviated in the case of the use of a liquid ring. Indeed, in this case, by the contracting of the diameter of the centrifuged annular piece, the reaction forces of the hearing which balance the centrifugal pressure, are not removed as in the case of a solid bearing.

In the accompanying drawings:

Figure l is a sectional view of a mold structure adapted for practicing the method of the invention.

Figures 2, 3 and 4, respectively, are sectional views similar to Figure 1, illustrating modified forms of the apparatus exemplified in Figure 1.

Figure 1 of the drawings shows in section a device for the centrifugal continuous casting between two concentric moulds. In this figure, 1 represents the interior mould, 2 the exterior mould, 3 a supply chamber, 4 the solidified centrifuged annular piece, 5 the liquid ring. If h is the height of the heavy metal necessary to counter balance the centrifugal pressure exerted by the height of liquid steel H and if r is the shrinkage, it is seen that the pressure exerted by the heavy liquid when the centrifuged annular piece has accomplished its shrinkage will correspond to a height of heavy metal equal to (h-r). As r is normally much smaller than h, the backpressure exerted on the annular piece by the heavy metal will not be appreciably reduced by the shrinkage and the danger of fissuring will then be considerably reduced with regard to a solid mould.

However, according to the invention, the back-pressure may be made more effective by creating a circulation of the metal of the ring and by controlling by means of bafiles the rate of discharge of the metal in the ring. So, a dynamic pressure, bound to the flow of heavy metal in circulation is added in the ring to the static pressure resulting from the centrifuging, so that the resulting pressure in the mould increases progressively during the shrhflrage.

The realization of the process of the invention may be achieved in various ways. As a nonlimiting example, certain modes of realization of the invention which are particularly interesting by their simplicity will be described by showing in each case how the regulation of the exterior diameter of the centrifuged annular piece may be realized, in spite of the unavoidable variations 'of the conditions of the operation due for example to the wear of the solid part of the mould, to the variations of the steel level in the supply chamber, to the variations of the flow and to the variations of temperature and of rotating speed.

The simplest method consists, according to the invention, in pouring into the supply chamber of the mould together with the steel, small quantities of heavy metal in liquid or even solid condition. Such a system may be compared with a simple lubrication of the mould by afirmof heavy liquid metal. But in addition'to the lubrication properly so called, this heavier metal encircles and exerts a confining on the exterior diameter of the annualpiece, an increasing of the rate of supplying of heavy metal necessarily producing a certain reduction of this diameter. This simple system however presents some disadvantages due to the fact that the heavy metal must pass through the melting steel. Consequently, the result is that there are more important losses by evaporation and by reaction with the impurities present in the steel." Especially there .is a possibility of inclusion of the heavy metal in the steel by imprisonment in the dendrites of the steel during :the crystallization. I

A relatively improved form of the invention is illustrated in Fig. 2 where parts identical to those of the preceding embodiment are designated by similar reference characters. In this form, according to the invention, the exterior mould is shaped in the form of a cup which is supplied with heavy metal 6 through one or several chan nels exterior to the steel 3 through a circular supplying chute 7 rotating with the mould which is cooled by not represented devicese.

A leakage flow forming a lubricating film escapes between the solidified annular piece and inner periphery of a sleeve on cup 8. This edge will be more or less wide and tapered to the profile naturally formed by the centrifuged annular piece during its shrinkage.

The rate of supply of heavy metal must counter- I balance the leakage flow to allow obtaining the desired exterior diameter of the centrifuged circular piece. Any variation of the supplying rate of flow gives rise to. a variation of the pressure in the ring and consequently a variation of the diameter of the annular piece. These variations are automatically balanced by a variation of the leakage-flow, which will normally increase or decrease with the pressure variations in the. ring.

" It is thus a self regulating system. This system can itself be controlled by measuring the forceexerte'd by the external mould on its hearings in the direction of the rotational axis. This force results directly from the ii'riction forces exerted by the centrifuged annular piece on the edge .of the cup; Then it suflices, according to the invention, to regulate the supplying flow to maintain '1 this force at an acceptable constant value, either by manual regulation or'bythe intervention of any suitable regulation system. It isimportant, insuch 'a systerm, to minimize the effect that "sudden variations of the 7 steel level in the supply chamber could produce on the diameter of the annual piece. To this ettect, a simple means consists in giving a slight section to the channels supplying the ring with heavy metal. Indeed, it is enough that in the communicating'vessels formed by v the channels and the liquid ring the'surface of the ring should be very much greater than the channel section circular piece placed at the beginning of the mould,

where the solidified steel is still very malleable. On the other part of the m0uld, the ring is reduced to a'simple lubricating film. e V

For a constant supplying flow to the ring 5 of heavy metal, the variations of the steel level have almost immediate consequential efifects on' the ring flow. For example, an increasing of the steel level reduces the how to the encircling The level in .the'supplying channel rises rapidly, forming in the ring a back pres sure which opposes the tendency; of the diameter of the circular piece 'to grow. a V V l This system has the addedadvantage of reducing the delay in the self regulating action. Moreover, this systern allows thesameadjuistment oi the'diameter of the circular pie eeby action on the rateof supply 'o'f the' heavy metal.

" n is een that me; adj asgsrome internal diameter ofLtheQliquid ring may be, accomplished by a leakage flow which must be recovered. 1 Recovery may bejaccomplished by following device, as shown-Vin 'Figure 85. steel, including ,lead, bismuth, silver and alloysof these elements, and circulating said molten. metal into and 7 out at the extremity of a gutter 9 situated at the mould end. a r

This sheet is collected by a fixed circular chute 10, the shape of said chute being conceived to'receive the metal jet and at the same time to avoid the throwing out of the metal and to absorb its inertia. a

The chute has for example a spiral shape. The metal isv collected below the chute, for return to the mold by'suit able means, not shown; The chute 10 may have, if needed, a circular movement, by fixing it on themould. When the chute is fixed on the mould, it retains the collected metal under the influence of the centrifugal force. A relatively low pressure 'will then. be sulfi'cient to bring backthe heavy metal to .thesupplying channel of the mold.

According to'the importance of the leakage flow, two principal modes iofjcirculation of-theheavy metal may be considered.

In thefirst mode, the metal constituting the liquid ring is not systematically changed and the leakage fiow' is the one which is exactly necessary for the regulation above mentioned. p p 7 f t :The steel'is' cooling down by conduction asin the case of esblid'mould. To go'from steel-to the solid mould, theheat must simply cross. through the intermediary sheet of-heavy metal. The conductivity of the selected metal and the thickness of'the liquid sheet are then important factors for the cooling. .The design of the external mould must also be carefully executed and cooling fiangesiin amaterial with good conductivity of the heatwill. be eventuallyused as shown at 11 in Figure 2.

' .In the second mode, the metal constituting theliquid ring is'rapidly changedand then the'steel is cooled down both by conductivity, as inthe first mode, and by the heating of the heavy metal in circulation. g r i To obtain the desired eifect, it is necessary to have sufficiently high'flowspsince the specific heat .of the used metals generally is. low. One must also pay attention to create high relative speeds of the heavy metal at the contact with its steel. This can be especially realizedbyan appropriate baffling. U In this case, the liquid ring will be supplied by a'complete device of circulation, the temperature and the flow of which are regulated. j

This device may obviously be provided with accumulators, regenerators and all other apparatus generally used to assure the previous purposes. Besides, thecooling device may be made as a heat recovering device in order to recover energy in every interesting form.

What we claim is: t V r 1.' A method for the centrifugal continuous casting of steel in a mold which consists in interposing a ring of molten metal heavier than steel between the steel and the wall of the mold, wherein the said ring ofmolten metal is formed by adding small quantities of molten metal to the liquid steel poured into the mold, including the step of regulating the diameter of the centrifuged circular piece by varying the rate of addition of'the heavy metal to the steel.

2. A method ,for the centrifugal continuous casting of steel in a mold which consists in jinterposing a ring of molten metal heavier than steel. between thelsteel and the wall of the mold, wherein the said ring of molten-metal is formedby adding small quantities of molten metal to the liquid steel poured into'the mold, said molten metal being chosen from the group: which does not alloy with through themold whereby same is dischargedfrom the mold, including the step of regulating the diameter of the centrifuged casting ,of steel by" varying the rate of addition of molten metal to the-steel.

" the'end of'the mould the leakage thrown out by '3. A method as claimed in claim 2, including'the step of collecting the molten metal of the annular ring at the mold exit and'recirculating same through the mold. v

4. A method as claimed in claim 3, including the step of cooling the said heavy metal of the annular ring during its circulation.

5. A method as claimed in claim 4, including the step of accelerating the cooling of the steel by a rapid circulation of the said metal of the annular ring.

References Cited in the file of this patent UNITED STATES PATENTS 1,831,310 Lindemuth Nov. 10, 1931 15,912 of 1891 22,708 of 1895 Enrich June 21, 1932 Rossi June 14, 1949 Fromson July 17, 1956 FOREIGN PATENTS Great Britain Aug. 20, 1892 Great Britain Nov. 21, 1896 

